Around 3000 new apartments are now being built in Auckland, a 12 per cent increase in stock.

New builds, with today's construction standards, are selling off-the-plans at $7000/sq m to $10,000/sq m, the report says.

"Investors in the apartment market tend to do best out of the cheapest option - studios. This is because even the smallest rent rise impacts highest on the most modest exposure. Rents will rise again as the economy and immigration continue to grow," the report says.

In 1991, Auckland had only about 228 apartments spread across just eight inner-city buildings. Now, 26,000 apartments are in 460 buildings.

"Many of these suites are 10 to 20 years old," the report says, pointing to refurbishment as an option to increase rental income and sale price.